Re: [HACKERS] [PATCH] Generic type subscripting

From: Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
To: Dian M Fay <dian(dot)m(dot)fay(at)gmail(dot)com>
Cc: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, David Steele <david(at)pgmasters(dot)net>, Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Fetter <david(at)fetter(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Oleksandr Shulgin <oleksandr(dot)shulgin(at)zalando(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] [PATCH] Generic type subscripting
Date: 2021-01-19 14:25:14
Message-ID: 20210119142514.nkevvvf7a2ux4553@localhost
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> On Thu, Jan 14, 2021 at 12:02:42PM -0500, Dian M Fay wrote:
> > Other than that, since I've already posted the patch for returning an
> > error option, it seems that the only thing left is to decide with which
> > version to go.
> The trigger issue (which I did verify) makes the "no update" option
> unworkable imo, JavaScript's behavior notwithstanding. But it should be
> called out very clearly in the documentation, since it does depart from
> what people more familiar with that behavior may expect. Here's a quick
> draft, based on your v44 patch:
> <para>
> <type>jsonb</type> data type supports array-style subscripting expressions
> to extract or update particular elements. It's possible to use multiple
> subscripting expressions to extract nested values. In this case, a chain of
> subscripting expressions follows the same rules as the
> <literal>path</literal> argument in <literal>jsonb_set</literal> function,
> e.g. in case of arrays it is a 0-based operation or that negative integers
> that appear in <literal>path</literal> count from the end of JSON arrays.
> The result of subscripting expressions is always of the jsonb data type.
> </para>
> <para>
> <command>UPDATE</command> statements may use subscripting in the
> <literal>SET</literal> clause to modify <type>jsonb</type> values. Every
> affected value must conform to the path defined by the subscript(s). If the
> path cannot be followed to its end for any individual value (e.g.
> <literal>val['a']['b']['c']</literal> where <literal>val['a']</literal> or
> <literal>val['b']</literal> is null, a string, or a number), an error is
> raised even if other values do conform.
> </para>
> <para>
> An example of subscripting syntax:

Yes, makes sense. I've incorporated your suggestion into the last patch,

Attachment Content-Type Size
v45-0001-Subscripting-for-jsonb.patch text/x-diff 45.6 KB
v45-0002-Filling-gaps-in-jsonb.patch text/x-diff 21.4 KB
v45-0003-Replace-assuming-a-composite-object-on-a-scalar.patch text/x-diff 5.6 KB

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